The invention relates to a process for the purging of flue gases containing acidic components, in particular sulfur dioxide, wherein the purging is effected in a washing fluid containing ammonia.
A series of processes is known, based upon desulfurization using ammoniacal solutions. In these processes various equilibrium reactions simultaneously occur in the washing tower, for instance the following: EQU SO.sub.2 +2NH.sub.3 +H.sub.2 O.revreaction.(NH.sub.4).sub.2 SO.sub.3 ammoniumsulfite EQU CO.sub.2 +2NH.sub.3 +H.sub.2 O.revreaction.(NH.sub.4).sub.2 CO.sub.3 ammoniumcarbonate EQU (NH.sub.4).sub.2 SO.sub.3 +1/2O.sub.2 .revreaction.(NH.sub.4).sub.2 SO.sub.4 ammoniumsulfate
As appears from these equations, a certain proportion of ammoniumsulfate is formed in the wash solution, irrespective of either flue gas concentration and oxygen content or operating temperature.
While the pH value of ammoniumsulfite and ammonium carbonate is between 7 and 8, the pH of a pure ammoniumsulfate solution is about between 4 and 5.
Other known processes for the desulfurization of flue gases determine the amount of ammonia to be added by the pH measured in the washing tower (West German published application No. 24 31 130). While in principle this kind of control is possible, it has the critical disadvantage that it can be effectively used only with low ammonium carbonate contents. In this connection reference is made to the FIGURE 1.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.